Add Mercedes to the very short list of companies trying to figure that out. On Monday, ahead of the Frankfurt Motor Show, Mercedes-Benz announced that it had successfully "driven" an autonomous vehicle 62 miles on German city streets and highways in August.

Mercedes' autonomous car, called the Mercedes-Benz S500 Intelligent Drive research vehicle, is on display this week in Frankfurt. The car has minor modifications, including three added long-range radar systems (two on the front, one on the back), four added short-range radar systems (one on each corner), and two cameras (one forward-facing, one rear-facing). The rear-facing camera scans the environment and compares it with a pre-loaded 3D "smart map," which is supplied by Nokia--no, not Google.

Nokia will supply navigation data

Nokia announced Monday that it will be working with infotainment platform-builders Magneti Marelli and Continental for its new Here Auto/Here Connected Driving connected car suite. It also announced that it is working with Mercedes on "smart maps," which are currently for use in connected cars, but will ultimately be used for self-driving cars.

"Based on the particular requirements of autonomous vehicles, this map includes precise road data that go beyond traditional maps," Nokia said in a statement. "Including the number and direction of lanes, traffic signs along the route, and even exact coordinates of traffic lights."

So what does all of this mean for the future of self-driving cars? Well, even Mercedes admits there are still many issues to work out, such as how autonomous vehicles will communicate with other vehicles on the road, and how quickly the public (read: lawmakers) will be able to accept self-driving vehicles.

A year ago, in September, Google CEO Sergey Brin suggested that autonomous vehicles will be ready for "ordinary people" in less than five years (by 2017). At CES in January, Audi showed off a self-parking car and claimed the technology would be ready in the next 10 years. And on Sunday, Mercedes' parent company Daimler AG said it aims to launch a self-driving car by 2020, the same year Nissan promises to do the same.